Process of cyanoethylating cellulose in the presence of salts



Jan. 23, 1962 N. M. BIKALES 3,

PROCESS OF CYANOETHYLATING CELLULOSE IN THEPRESENCE 0F SALTS Filed Jan. 6, 1958 3 Sheets-Sheet 1 0|.LVH NV g I 2 or no rw IO 1- :0 m o l I I I l I I l I E -I B I o 0: I r 2 2| E o:

PARTS OF NdI/IOO PARTS OF 2% NoOH INVENTOR. NORBERT M. BIKALES E ham ATTORNEY Jan. 23, 1962 N. M. BIKALES 3,013,156

PROCESS OF CYANOETHYLATING CELLULOSE IN THE PRESENCE OF SALTS Filed Jan. 6, 1958 3 Sheets-Sheet 3 I O D Z L -8 1:

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ATTORNEY 3,018,156 PRUCESfi @F CYANSETHYLATHJG CELLULQSE IN THE PREEN CE 9F SALTS Norbert M. Bikales, Stamford, Conn, assignor to American (Jyanatnid (lompany, New York, N.Y., a corporation of Maine Filed Jan. 6, 1958, Ser. No. 709,439 it) Claims. (Cl. 8li6.2)

This invention relates to an improved method for the cyanoethylation of cellulose, and particularly cellulosic fibers and fabrics such as cotton.

The cyanoethylltion of cotton textile fibers has achieved a great deal of interest in recent years. Most of the work has been done on cotton and products of improved characteristics have been obtained, including resistance to mildew, heat-resistance, abrasion-resistance and, in some cases, improved strength. Improved dyeability for certain types of dyes has likewise been noted. For textile fibers such as cotton, viscose, rayon and the like, it is necessary that the cyanoethylation be limited so that not substantially more than one cyanoethyl group on the average is introduced per anhydroglucose building block of the cellulose. Degrees of cyanoethylation are usually measured by determining the nitrogen content of the oyanoethylated product. For textile fiber uses, this should range from about 2% nitrogen to not more than 7.

Another field in which cyanoethylated cellulose is of importance is as a plastic material. in such cases the cellulose is cyanoethylated to a much higher degree, from in excess of 7% nitrogen up to complete cyanoethylation in which all three hydroxyl groups of the anhydroglucose building block are cyanoethylated. Complete cyanoethylation corresponds to a nitrogen percentage of about 13%. These highly cyanoethylated products are soluble in organic solvents and are usually dissolved and cast as films or extruded as fibers. They may also be molded because of their thermoplastic nature. in general, the highly cyanoethylated celluloses can be formed into products which have desirable electrical properties. Thus, they exhibit a very high dielectric constant. This dielectric constant is higher than that of any other organic plastic, and this property renders the material useful for electrical components.

in the highly cyanoethylated material, cotton or at least cotton in the form of textile, is not the most important source of cellulose as it is in the case of the lower cyanoethylated products in which the physical form and constitution of the textile fiber is retained. On the contrary, in the case of highly cyanoethylated material which is to be dissolved in organic solvents or molded, the physical form of the original cellulose is of no great significance and therefore other sources, such as alpha-cellulose fibers, cotton linters, wood cellulose, regenerated cellulose scrap, and the like become important since these products are often much cheaper than high grade textile fibers, either of cotton or of other cellulose forms, such as rayon and the like.

conventionally, cyanoethylation is effected by reaction of the cellulose with strong alkalies, such as sodium or potassium hydroxide, and acrylonitrile. The early work which is typified by US. Patent 2,786,258, for the most part used a so-called two-step process in which the cellulose was first treated with a strong alkali, excess solution removed, and then the material reacted, usually at a somewhat higher temperature, with acrylonitrile. By this method, it is perfectly possible to cyanoethylate cotton textile fibers to produce a product of satisfactory commercial characteristics. However, the original process was very wasteful of acrylonitrile. Acrylonitrileloss is generally measured in the art by the so-called AN ratio. This is the ratio of acrylonitrile wasted, more particularly by by-product reactions such as the reaction with water to form [3,5-oxydipropionitrile, divided by the acrylonitrile which is actually introduced into the cellulose in the form of cyanoethyl groups. In the early work, as exemplified by the above patent, AN ratios from slightly below 5 for insufficiently cyanoethylated material up to AN ratios of 20 or more for cyanoethylated material having a higher nitrogen content were the best that could be achieved. An AN ratio of 20 represents a loss of 20 times as much acrylonitrile as that which reacts with the cellulose; in other words, based on the unrecoverable acrylonitrile, the yield is slightly under 5%. As acrylonitrile is one of the more expensive reagents used, such high AN ratios rendered the process commercially unattractive, as the costs were excessive.

A great improvement on the original twostep cyanoethylation process was made by a so-called one-step process in which the strong alkali and acrylonitrile were both compacted with the cellulose such as cotton before the temperature was raised to the point at which any significint degree of reaction took place. This process permitted improved AN ratios of the order of 2 in the case of textile fibers where the cyanoethylation does not produce a nitrogen content of greater than about 5. This process has been practiced on a commercial scale. Improvements in the efliciency of the process are therefore still desirable.

Another factor in the cyanoethylation process which is of vital importance in the case of many highly cyanoethylated products is the degree of hydrolysis of cyanoethyl groups in the cellulose. It is obvious that the reaction conditions, namely, presence of water, strong alkali, and moderately elevated temperatures permit the hydrolysis of cyanoethyl groups. In fact, the whole cyanoethylation process might be considered as a compromise between competing reactions, that i to say, competition between introduction of cyanoethyl groups and hydrolysis. The hydrolysis reaction results in formation of carboxyethyl groups in the cyanoethyl cellulose.

The hydrolysis reaction is, of course, accelerated by temperature and by concentration of strong alkali, as well as by time, during which the reaction is taking place. As will be pointed out below, the present invention permits a drastic acceleration of reaction rate which not only permits extraordinarily low AN ratios, even below 1 in certain instances, but it also permits using much milder reaction conditions and so permits a marked reduction in the degree of hydrolysis. As pointed out above, this latter advantage is not so important with the textile fibers which are cyanoethylated only to a lower degree, but it is of vital importance with the highly cyanoethylated fibers where, of necessity, reaction conditions have to be more drastic.

Essentially, the present invention depends on a discovery that a particular class of salts which are substantially unreactive with acrylonitrile under ordinary cyano- Concentra- Solubility Nature of Salt tion, g. salt/ Temp., of AN, g./ 100 g. 1120 C. 100 g. H2O

None 24. 5 8 Sodium Iodide 150 24. 18

one 50 9. 1 Sodium Iod1de 150 50 16 None 32. 5 8 3 Sodium Thiocyanate. 100 32. 5 97 It will be noted that the typical hydrotropes are for the most part neutral salts, that is to say, they are salts of strong acids. It is not absolutely essential that the hydrotrope be completely neutral in the sense that when it is dissolved in Water the pH is exactly 7. A very slight departure from complete neutrality, such as the slightly alkaline reaction of sodium benzoate does not interfere. However, strongly alkaline salts such as sodium phosphates are not useful in the present invention and of course, strongly acidic salts would also not be useful as they would destroy the effect of the caustic alkali used in the reaction. The hydrotropic salts are not acting because they are alkaline catalysts, for in the case of the few which display very slight alkalinity, such as sodium benzoate, the alkalinity is insufficient for useful catalysis and in fact, the effectiveness of such hydrotropes is not as great as those that are completely neutral, such as the alkali metal iodides, thiocyanates, etc.

While the salts used in the present invention are all hydrotropes for acrylonitrile, it is not intended to limit the invention to the theory that the Whole effect is due to their hydrotropic nature. It is not known just what the mechanism is, but it is reasonably certain that hydrotropicity is only one factor. This is shown by the fact that the effectiveness of the different salts is in no sense directly proportional to their hydrotropic powers. It seems probable therefore that other factors play an important role. Thus for example, it appears that the swelling effect of the salts on the cellulose is an important consideration and may well exert a greater effect in the actual reaction than the hydrotropicity of the salt used. Other factors may also be present in the reaction, and the invention is therefore not limited to theory.

The increase in reactivity, as measured by increased cyanoethylation under fixed conditions, is so extreme with some of the salts used that when standard reaction times of the order of 45 minutes are employed cyanoethylation goes far beyond the stage of physically unchanged textile fibers. In other words, reaction conditions which would normally produce an unchanged textile fiber with a nitrogen content of from 3 to 5 or 6% will produce highly cyanoethylated products with nitrogen percentages well beyond 7%. The present invention presents advantages in shortening the reaction time and producing the marked savings in acrylonitrile which have been referred to above. In the case of higher cyanoethylated products, the advantages of the present invention may, in some cases, be used to moderate the intensity of the reaction conditions such as temperature, concentration of alkali and the like. In each case, with each kind of cyanoethylated product, the compromise will be chosen which gives the best results for that product. It is thus an important advantage of the present invention that it is extremely flexible and better results can be obtained Without any undesirable characteristics.

The amount of salt added can be varied over enormous ranges. Thus, for example, sodium iodide may be used in amounts from as little as 20 g. or less per g. of sodium hydroxide solution up to amounts as high as 230 g., which is a saturated solution at 55 C. In general, the most active salts, of which sodium thiocyanate is typical, reach a very favorable acrylonitrile ratio quite early. Additional amounts reduce the acrylonitrile ratio only a little but result in an increased rate of cyanoethylation. In the case of sodium iodide at 55 C., and 45 minutes duration, the maximum degree of cyanoethylation is reached at about 100 g. per 100 g. of NaOH solution. In general, it is desirable to use as little of the salt as is possible and still obtain the desired degree of cyanoethylation in a reasonable time with a good acrylonitrile ratio. The relatively large range of concentrations which are usable is an important operating advantage of the present invention. Very precise control of concentration is not necessary. No concentration limits can be given which are applicable to all of the salts added for, as would be expected from the greatly different effects on reaction rate, from the varying solubilities, and from the optimum concentrations from the standpoint of cost, product characteristics and acrylonitrile ratio differ with different salts.

The economic importance of the greatly lowered acrylonitrile ratios obtained by the present process is self-evident. However, the marked increases in reaction rate which is obtainable with the most active salts such as sodium iodide, sodium perchlorate, sodium thiocyanate, and the like makes it possible to cut the reaction time down to such an extent that a continuous rather than a batch process becomes practical. This is an important economic advantage for the most active of the salts used in the present invention. Even if batch processes are used, this advantage can still be notable because the shorter reaction time makes possible increases in the output of the equipment used.

The invention will be described in greater detail in conjunction with the following specific examples in which the parts are by weight unless otherwise specified. In these examples, the degree of cyanoethylation is expressed as added percent nitrogen.

The invention will also be described in conjunction with the following drawings in which:

FIG. 1 is a graph showing variations of nitrogen percentage and AN ratio with varying amounts of sodium iodide all other conditions being held constant;

FIG. 2 is a graph of variations of nitrogen content and AN ratio with varying amounts of sodium thiocyanate all other conditions being held constant; and

FIG. 3 is a similar diagram with a different concentration of caustic soda.

Example 1 Five parts of cotton yarn was treated with 270 parts of an aqueous solution of 2 parts sodium hydroxide and parts of sodium iodide for thirty minutes and excess solution removed until 18.6 parts of wet cotton remained. The cotton was then added to 80 parts of technical grade acrylonitrile at a temperature of 55 C. and reacted for 45 minutes. Thereupon neutralization was effected with glacial acetic acid and the cotton washed with water and the amount of acrylonitrile in the washings determined. The cotton was then dried and analyzed for nitrogen. The added nitrogen percentage was 9.3 and the AN ratio was 0.9.

The same amount of cotton yarn was treated under the identical conditions except that the sodium hydroxide solution contained no sodium iodide and that the same amount of sodium hydroxide solution was left in the cotton. The added nitrogen was 3.9% and acrylonitrile ratio was 4.9.

Example 2 As the reaction rate shown in Example 1 was so high that an excessive degree of cyanoethylation resulted, the concentration of sodium iodide was progressively decreased, the other conditions remaining the same. The added nitrogen percent was 3.5 with 10 partsof sodium iodide, 7.0 with 50 parts and reached about 9.7 at 105 parts. The acrylonitrile ratio was 3.0, 1.3 and 0.3 respectively.

The data from Examples 1 and 2 appears in graphical form on FIG. 1. The graph clearly shows that with an increase of sodium iodide the AN ratio at first drops rapidly and then reaches a substantial minimum. The effect of the largest amount of sodium iodide used was so great that some of the cotton actually dissolved in the excess acrylonitrile which made an exact determination of the AN ratio very difficult and the value given in Example 1 represented a maximum. The experimental error hereis, however, large enough so that it probably does not indicate a significant difference in AN ratio over that measured for 105 parts of sodium iodide. For this reason, the extrapolation of the AN ratio line is shown as a broken line in FIG. 1. A similar situation prevails in FIG. 2.

Example 3 Effects of time and temperature were tested with various amounts of sodium iodide. The other conditions of the process were, however, not changed. The results are as follows: with 200 parts of sodium iodide at 40 C. the added nitrogen was 2.9% and the acrylonitrile ratio was 1.4.

A test was made at 65 C. using 100 parts sodium iodide and a short time of 5 minutes. The results were 3.3% added nitrogen and an acrylonitrile ratio of 1.1.

A run at standard temperature of 55 C. with 200 parts of sodium iodide was carried out in minutes. The added nitrogen was 2.3%, acrylonitrile ratio 2.0. It is obvious that for these conditions 10 minutes is too short for optimum results. The next run was with 100 parts of sodium iodide at standard temperature for minutes. This gave an added nitrogen percentage of 4.1 substantially optimum for textile uses, and an acrylonitrile ratio of 0.6.

Example 4 The efiect of varying the amount of caustic soda and iodide solution retained by the cotton was investigated by repeating the conditions of Example 1 except that the cotton was squeezed as dry as possible, leaving 6 parts of solution on 5 parts of cotton. The added nitro gen percent was 5.7 and the acrylonitrile ratio 1.1. It will be apparent that squeezing out the cotton to a greater extent did not give quite as good results as were obtainable with shortened time and/ or with lower concentrations.

Example 5 The effect of sodium iodide was determined in a onestep process in which 5 parts of cotton yarn was introduced in 80 parts of acrylonitrile at 55 C. There was then added 16.5 parts of a solution resulting from saturating 5 parts of 2% sodium hydroxide with sodium iodide. A control experiment was carried out in which the sodium iodide was eliminated. Both experiments used a time of reaction of 90 minutes. The added nitrogen was .7% for the control with an acrylonitrile ratio of 8.8. The process using the sodium iodide gave an added nitrogen percent of 5.2 and an acrylonitrile ratio of 1.6.

series of salts.

Example 6 The procedure of Example 1 was followed using a In each case, with the exception of sodium perchlorate, the substantially saturated solution was obtained at room temperature but the concentrations of salts of course varied and the weight pick-up by the cotton of course also differed, but by a corresponding factor. The first run was with potassium iodide. The weight pick-up by 5 parts of cotton was 11.8 parts. The increased nitrogen percentage was 11.5. It was not possible to obtain an accurate acrylonitrile ratio because the swelling power of the potassium iodide was so great that the, cotton was gelatinized and partially dissolved in the acrylonitrile. The ratio, however, was much lower than for the control.

Sodium thiocyanate with a pick-up of 11.4 parts, gave added nitrogen 10.9%, acrylonitrile ratio less than 2.2. It was possible to obtain an absolutely accurate ratio because of the interference of thiocyanate in the acrylonitrile analysis.

Sodiumbenzoate with a pick-up of 7.1 parts, gave added nitrogen 9.1% and AN ratio of 2.3.

fSodiumpara-toluenesulfonate with a pick-up of 3.3 parts, g'ave added nitrogen 6.3% and AN ratio of less than 2.6. i

Sodium xylenesulfonate with a picl -up of 7.5 parts, gave addednitrogen 8.2% and AN ratio of 2.7.

Sodium perchlorate with a pick-up of 10.0 parts gave added nitrogen 11.0%. In this case, the solution employed was not saturated, yet the effect was so great that the cotton partially dissolved in the acrylonitrile.

Example 7 The procedure of Example 1 was repeated using varying amounts of sodium thiocyanate instead of sodium iodide. The results are shown graphically on FIGURE 2. With the highest amount of sodium thiocyanate used, difiiculties were again encountered with the analytical procedure, and the exact AN ratio is therefore not shown.

, The value of 2.2 is probably a maximum. The same statement as was made with respect to FIG. 1 is applicable here.

Example 8 The procedure of Example 7 was repeated but the concentration of sodium hydroxide was cut in half, i.e., 1% NaOH before dilution by the salt. Again, varying amounts of sodium thiocyanate were used and the results are shown graphically in FIG. 3.

Example 9 Ten parts of cotton yarn was treated. with 200 parts of an aqueous solution of 2 parts of sodium hydroxide and parts of sodium iodide for thirty minutes and excess solution removed until 20 parts of wet cotton remained. The cotton was then exposed for one hour to acrylonitrile vapors at 100 C. Thereupon neutralization was efiected with dilute aqueous acetic acid and the cotton washed with water and the amount of acrylonitrile in the washings determined. After drying, the added nitrogen percentage was 4.3 and the acrylonitrile ratio was 3.7. A

control experiment under these conditions in which no sodium iodide was used and the same amount of sodium hydroxide solution was left in the cotton gave 2.0% added nitrogen and an acrylonitrile ratio of 6.4.

Example 10 A number of experiments were carried out to obtain cyanoethylation of cotton yarn within the nitrogen percentages of about 3-6%, in which range the cotton fibers retained their physical characteristics as textile fibers. A

total of eight runs were made with control runs in the absence of the salt for all but 2, 3 and 4. In the case of runs 3 and 4 the pretreated cotton was squeezed as dry as possible, resulting in somewhat lower nitrogen percentages. The conditions and results obtained appear in the following tablet precipitated product was thoroughly washed with water and dried. Analysis showed a nitrogen content of 12.6%,

g. of Salt Initial Time of Tern- AN per 100 g. NaOH Total Reacpcrature Nitrogen AN Ratio Run Salt of NaOH Concen- Pickup, tion, Reac- Percent Ratio in the Solution tration 1 Percent min. tion, bsence C. of Salt 1 100 2. 200 15 55 4.1 0.6 2 100 2. 0 200 65 3. 3 1. l 3 200 2. 0 120 4 5 55 5. 7 1. l 4 50 2. 0 70 55 3. 7 0. 6 5 50 2. 0 150 15 55 5. 0 1. 2 6 25 l. 0 125 45 55 5. 2 1. 3 7 25 2. 0 125 15 55 4. 1 1. 5 8 CsH5COONa 50 2.0 150 15 55 4.6 2.3

1 Before dilution by additive.

Example 11 corresponding to virtually complete substrtutlon of the A 4-inch wide 80 x 80 bleached cotton percale was first steeped in a bath containing a solution of 5% aqueous sodium hydroxide and an equal weight of potassium iodide. The cloth was squeezed in a pad roll and exposed in a closed chamber to acrylonitrile-water vapors at reflux. The temperature varied from 7075 for the most part remaining at about 71 C. A series of runs were made, the nitrogen content varying from an average of about 3.5% in 2 minute runs to 6.5% in 3.5 minute runs.

When the salt was omitted, substantially longer times were required to obtain the same nitrogen percentages and the AN ratios were higher.

The padding procedure was then repeated under the same conditions, but using sodium thiocyanate instead of the potassium iodide, and again in 2 minutes the nitro gen content averaged about 3.5%.

Example 12 The so-called one-step process which has been referred to above, was investigated with varying amounts of sodium thiocyanate. Skeins of 5 parts each of cotton yarns were rapidly agitated in liquid acrylonitrile with the addition of a small amount of sodium hydroxide-sodium thiocyanate solution. One run was also carried out Without any sodium thiocyanate. After the addition of the alkaline solution, the mixture was vigorously agitated for 10 minutes at room temperature to give an even distribution on the cotton yarn. Thereupon the temperature was raised to 50 C. and maintained for 40 minutes. The following table shows the results obtained in the five runs.

parts of parts of Average 4% NaSON percentN AN Ratio a0 It will be noted, that the increase in reactivity and decrease in AN ratio while quite marked, were not as pronounced as in the earlier examples Where a two-step process was used. This result was not surprising as the limited amount of the aqueous phase reduced the swelling of the cotton and therefore the reactivity of cellulose in this onestep process.

Example 13 hydroxyl groups of cellulose. The modified cellulose is soluble, among others, in acrylonitrile, dimethylformamide, dimethylsulfoxide, N-methyl-Z-pyrrolidone, pyridine, from which it is reprecipitated as films.

Example 1 4 Sixty parts of cotton linters were immersed in 2400' parts of acrylonitrile. A solution consisting of 3 parts of sodium hydroxide, 50 parts of sodium thiocyanate and. 97 parts of water was added gradually at room temperature while the mixture was being vigorously stirred- Fifteen minutes after completion of the addition, the temperature was raised to reflux (about 7075 C.) and samples were withdrawn at intervals, neutralized, precipitated, washed with water, dried and analyzed. The nitrogen contents were 5.6% upon first reaching reflux temperature, 10.5% after five minutes, 11.6% after 10 minates, 11.9% after 15 minutes and 12.0% after 30 minutes at reflux. The cellulose completely dissolved in the excess acrylonitrile when it reached a nitrogen content of about 11.8%, forming a very viscous and somewhat cloudy solution.

The AN ratio was determined after five minutes at reflux. It was 0.8, thus making this procedure commercially practical.

Example 15 One hundred and ten parts of viscose rayon staple was steeped at room temperature for 200 minutes in a solution consisting of 995 parts of Water, 5 parts of sodium hydroxide and 400 parts of sodium thiocyanate. The cellulose was then squeezed until it retained 244 parts of alkali solution, and immersed in 2000 parts of acrylonitrile. The temperature was then raised to reflux while the mixture was agitated. Fifteen minutes later, the cellulose had dissolved in the excess acrylonitrile forming a light tan, viscous solution. After one hour at reaction temperature, the mixture was neutralized and unreacted acrylonitrile recovered by steam distillation. The precipitated cellulose was then thoroughly washed with deionized water, dried and analyzed. It contained 11.8% nitrogen.

Discs, each weighing 35 grams, were molded from the product at 310 F. and 5350 p.s.i. The dielectric properties were then determined according to A.S.T.M. D 54T. The dielectric constant was found to be 16.6 at 60 c.p.s. (31 C.), as compared to 13.3 where no salt was used in the preparation. The dielectric loss factor was 0.465 as compared to 1.87 of cellulose prepared as above but omitting salt and using a correspondingly higher sodium hydroxide concentration, namely, 4%.

It will appear from the foregoing examples that improvements in the efficiency and hence cost of the process of cyanoethylation is obtained in every case by the use of salts as shown by the improved AN ratio.

This application is in part a continuation of my copending application 448,768, filed August 9, 1954, and now formally abandoned.

I claim:

1. In a process of partially cyanoethylating cellulose fibers wherein said fibers are reacted with acrylonitrile simultaneously with and in the presence of an aqueous solution of an alkali metal hydroxide under known conditions capable of producing the desired nitrogen content; the improvement whereby (a) the rate of introduction of cyanoethyl groups is selectively increased without increasing the rate of hydrolysis and (b) in obtaining the desired degree of cyanoethylation the weight of acrylonitrile consumed in side reactions is decreased; said improvement comprising: adding to said aqueous solution a water-soluble salt in amount by weight of from about one part of salt to about twenty parts of said aqueous solution up to a suflicient amount to substantially saturate said aqueous solution in said salt; said salt being a hydrotropic alkali metal salt of an anion selected from the group consisting of iodide, thiocyanate, benzenesulfonate, toluenesulfonate and Xylenesulfonate.

2. A process according to claim 1 in which the cellulose is in the form of textile fibers and the cyanoethylation reaction is stopped when the cyanoethylated textile fibers show a nitrogen content in the range from 2 to 7% and the textile fibers retain their physical form substantially unchanged and exhibit a high degree of mildew resistance as compared with the uncyanoethylated fibers.

3. A process according to claim 2 in which the hydrotropic salt is an alkali metal thiocyanate.

4. A process according to claim 3 in which the cellulose fibers are cotton textile fibers.

5. A process according to claim 2 in which the hydrotropic salt is an alkali metal iodide.

6. A process according to claim 5 in which the textile fibers are cotton textile fibers.

7. A process according to claim 1 in which the reaction is continued until the cyanoethylation has proceeded beyond a nitrogen content of 7% and the product is soluble in organic solvents and exhibits decreased hydrolysis of cyanoethyl groups.

8. The process according to claim 7 in which the hydrotropic salt is an alkali metal iodide.

9. A process according to claim 7 in which the hydrotropic salt is an alkali metal thiocyanate.

10. A process according to claim 7 in which the salt is an alkali metal xylenesulfonate.

References Cited in the file of this patent UNITED STATES PATENTS 2,289,039 Reichel July 7, 1942 2,375,847 HoutZ May 15, 1945 2,786,258 Compton Mar. 26, 1957 2,840,446 Compton June 24, 1958 FOREIGN PATENTS 515,855 Great Britain Dec. 15, 1939 OTHER REFERENCES Encyclopedia of Surface Active Agents, 1. P. Sisley, 1952, page 207.

Merck Index, 5th Edition, 1940, page 321.

UNITED STATES PATENT OFHCE CERTIFICATE OF CORRECTION Patent No, @618, 156 January 23 1962 Norbert M Bikales above numbered patfied that error appears in the hould read as It is hereby certi and that the said Letters Patent s ent requiring correction corrected below.

Column 6 line I9 after "was" insert not "0 Signed and sealed this 29th day of May 1962;

(SEAL) Attest: ERNEST w. SWIDER DAVID-L- LADD Commissioner of Patents Attesting Officer 

1. IN A PROCESS OF PARTIALLY CYANOETHYLATING CELLULOSE FIBERS WHEREIN SAID FIBERS ARE REACTED WITH ARCYLONITRILE SIMULTANEOUSLY WITH AND IN THE PRESENCE OF AN AQUEOUS SOLUTION OF THE ALKALI METAL HYDROXIDE UNDER KNOWN CONDITIONS CAPABLE OF PRODUCING THE DESIRED NITROGEN CONTENT; THE IMPROVEMENT WHEREBY (A) THE RATE OF INTRODUCTION OF CYANOETHYL GROUPS IS SELECTIVELY INCREASED WITHOUT INCREASING THE RATE OF HYDROLYSIS AND (B) IN OBTAINING THE DESIRED DEGREE OF CYANOETHYLATION THE WEIGHT OF ACRYLONITRILE CONSUMED IN THE SIDE REACTIONS IS DECREASED; SAID IMPROVEMENT COMPRISING: ADDING TO SAID AQUEOUS SOLUTION A 